Parameter design method and device for impedance correction device of direct-current power transmission system

Abstract

The invention discloses a parameter design method and device for an impedance correction device of a direct-current power transmission system, and the method comprises the steps: obtaining a voltage parameter and a harmonic parameter of an alternating-current system according to a constructed target direct-current power transmission system topology, and designing an amplitude-phase corrector parameter optimization model; in different operation modes, impedance characteristics of the alternating current and direct current system are obtained respectively; in response to the impedance characteristic, performing simulation through an amplitude-phase corrector parameter optimization model to obtain element stress of the amplitude-phase corrector in a corresponding fluctuation state; in the corrector configuration link, parameters of an amplitude-phase corrector are determined according to the voltage fluctuation ratio of the alternating current system and the operation power range of the direct current system, and the parameters are optimized based on element stress so as to configure the amplitude-phase corrector; and after the amplitude-phase corrector is configured, the corrector configuration link is repeated until the equivalent harmonic impedance of the direct-current power transmission system meets a preset system oscillation index. Harmonic oscillation in a direct-current power transmission system can be effectively reduced by optimizing parameters of the amplitude-phase corrector.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current transmission, and in particular to a parameter design method and device for an impedance correction device of a direct current transmission system. Background Art

[0002] The multi-source adaptive phase-commutated converter (SLCC) DC transmission technology is a new type of DC transmission technology that combines the technical characteristics of the grid-commutated converter (LCC) and the large-capacity static VAR filter (SVF). It integrates the mature technical accumulation of high voltage and high power of traditional DC transmission and the technical characteristics of new power electronic devices, adopts valve-side reactive power compensation and harmonic filtering technology, improves the adaptability of DC access to weak AC systems, reduces the safety hazards of converter transformers, reduces the risk of DC commutation failure, eliminates the amplitude and phase corrector field, reduces the equipment noise level, and saves the project area.

[0003] In scenarios such as new energy-SLCC and weak AC system-SLCC, a large number of power electronic devices have high-frequency switching operation characteristics, and the impedance of the entire power grid and SLCC DC interconnection system presents nonlinear characteristics. As the switching frequency increases, the control delay caused by measurement, communication and calculation links has an increasing impact on the response characteristics of the system, resulting in frequent wide-band oscillations such as medium and high frequencies. In order to solve such problems, a hardware suppression solution can be used to configure an amplitude phase corrector on the AC bus. However, the existing amplitude phase corrector has a poor effect on improving the impedance characteristics of the SLCC converter, resulting in the inability to effectively suppress harmonic oscillations, affecting the stable operation of the transmission system.

[0004] It can be seen that how to improve the amplitude and phase correction device has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] The present invention provides a parameter design method and device for an impedance correction device of a direct current transmission system, so as to solve the problem of how to improve the design of parameters of the amplitude and phase correction device, so as to improve the impedance adjustment capability of the amplitude and phase corrector and ensure the stable operation of the transmission system.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a parameter design method of a DC power transmission system impedance correction device, comprising:

[0007] According to the constructed target DC transmission system topology, the voltage and harmonic parameters of the AC system are obtained, and the amplitude and phase corrector parameter optimization model is designed;

[0008] Under different preset operation modes, respectively obtaining impedance characteristics of the AC and DC systems of the target DC power transmission system topology;

[0009] In response to the impedance characteristics, the component stress of the amplitude phase corrector under the corresponding fluctuation state is obtained by simulating the amplitude phase corrector parameter optimization model;

[0010] In the corrector configuration link, the initial parameters of the amplitude-phase corrector are determined according to the voltage fluctuation rate of the AC system and the operating power range of the DC system, and the initial parameters are optimized based on the component stress to configure the amplitude-phase corrector;

[0011] After the amplitude and phase corrector is configured, the corrector configuration step is repeated until the equivalent harmonic impedance of the target DC power transmission system topology meets a preset power transmission system oscillation index.

[0012] Furthermore, the design of the amplitude-phase corrector parameter optimization model includes:

[0013] Under the power frequency extreme, design a power frequency amplitude-phase corrector parameter optimization model according to the acquired rated voltage, steady-state voltage, and extreme voltage of the AC system;

[0014] A harmonic amplitude and phase corrector parameter optimization model is designed based on the acquired background harmonic voltage and harmonic current at the AC bus of the target DC power transmission system topology.

[0015] Furthermore, the impedance characteristics of the AC / DC system of the target DC power transmission system topology are obtained respectively under different preset operation modes:

[0016] Taking the AC bus of the target DC power transmission system topology as a port, obtaining a first impedance characteristic of the AC system within a preset frequency range under different disconnection modes; and

[0017] Obtain the second impedance characteristics of the wideband DC system under different operating modes.

[0018] Further, in response to the impedance characteristic, simulating the component stress of the amplitude phase corrector in the corresponding fluctuation state through the amplitude phase corrector parameter optimization model includes:

[0019] In response to the impedance characteristic, a first stress distribution generated by the AC system under an extreme power frequency condition is calculated by using the power frequency amplitude and phase corrector parameter optimization model;

[0020] The target switch in the harmonic amplitude and phase corrector parameter optimization model is closed / opened to obtain the second stress distribution generated by the AC system under the influence of harmonics.

[0021] Furthermore, the corrector configuration step further includes:

[0022] Calculating component constants of the configured amplitude and phase corrector according to the harmonic parameters;

[0023] The component constants are analyzed to optimize and adjust the parameters of the amplitude and phase corrector.

[0024] Furthermore, the voltage fluctuation rate is controlled within 1%.

[0025] Furthermore, the different disconnection modes include three disconnection modes N-0, N-1 and N-2 within the three-level section.

[0026] Furthermore, the different operation modes include bipolar operation, monopolar operation and monopolar metal operation.

[0027] Another embodiment of the present invention provides a DC power transmission system impedance correction device, which is applied to the parameter design method of the DC power transmission system impedance correction device, and the device includes: a multi-source adaptive DC power transmission system and the amplitude and phase corrector;

[0028] The multi-source adaptive direct current transmission system includes a grid phase-commutating converter, a commutating transformer and a filter;

[0029] The amplitude and phase correctors are arranged at both sides of the multi-source adaptive direct current power transmission system.

[0030] Furthermore, the amplitude-phase corrector is configured as a C-type amplitude-phase corrector composed of a high-voltage capacitor, a low-voltage capacitor, a reactor and a resistor connected in series and in parallel.

[0031] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0032] The embodiments of the present invention design amplitude-phase correction calculation models under different situations to determine the component stress of the amplitude-phase corrector to adjust the parameters of the amplitude-phase corrector under the response of extreme voltage and harmonic fluctuations and the impedance of the DC system. By comprehensively considering the background harmonic voltage of the AC system and the effects of the harmonic current injected by the converter, the amplitude-phase corrector component constants can be accurately calculated to achieve optimal parameter design. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of a parameter design method of a DC power transmission system impedance correction device in one embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of a calculation model of an amplitude-phase corrector under power frequency conditions in one embodiment of the present invention;

[0035] Figure 3 It is a schematic diagram of a calculation model of an amplitude and phase corrector under the action of harmonics in one embodiment of the present invention;

[0036] Figure 4 is a schematic structural diagram of a direct current transmission system in one embodiment of the present invention;

[0037] Figure 5 It is a schematic diagram of the structure of a C-type amplitude-phase corrector in one embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the description of this application, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the feature. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0040] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for illustrative purposes, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0042] An embodiment of the present invention provides a parameter design method for a DC power transmission system impedance correction device. For details, see Figure 1 , Figure 1 The figure shows a flow chart of a parameter design method for a DC power transmission system impedance correction device in one embodiment of the present invention, comprising the following steps:

[0043] S1. According to the constructed target DC transmission system topology, the voltage parameters and harmonic parameters of the AC system are obtained, and the amplitude and phase corrector parameter optimization model is designed.

[0044] This step is the process of constructing the topology and designing the amplitude and phase corrector calculation model. This embodiment takes into account the superiority of the multi-source adaptive commutation converter transmission system, constructs the topology structure based on it, and obtains the voltage parameters and harmonic parameters of the AC system in the topology.

[0045] As you can understand, voltage parameters include rated voltage, steady-state voltage, and extreme voltage. The highest steady-state voltage refers to the highest voltage value that the system may reach under normal operating conditions, while the lowest steady-state voltage refers to the lowest voltage value that the system may reach under normal operating conditions. Extreme voltage is the highest or lowest voltage value that may occur in the AC system under specific conditions (such as faults, lightning strikes, etc.).

[0046] Based on this, this embodiment designs a parameter optimization model of the power frequency amplitude phase corrector under the power frequency extreme according to the obtained rated voltage, steady-state voltage, and extreme voltage of the AC system. For details, please refer to Figure 2 , Figure 2 The figure shows a schematic diagram of the calculation model of the amplitude-phase corrector under power frequency conditions in one embodiment of the present invention. This embodiment aims to design an amplitude-phase corrector parameter optimization model based on power frequency conditions such as the highest / lowest steady-state voltage and the highest / lowest extreme voltage, so as to calculate the stress of the AC system under power frequency extreme voltage conditions.

[0047] Correspondingly, the harmonic parameters refer to the background harmonic voltage and harmonic current at the AC bus of the target DC transmission system topology. Therefore, this embodiment designs a harmonic amplitude and phase corrector parameter optimization model based on the acquired background harmonic voltage and harmonic current. It is worth noting that the background harmonic voltages of the AC system include at least 1 to 50 background harmonic voltages, and the harmonic currents include at least 2 to 50 converter injected harmonic currents.

[0048] Specifically, please refer to Figure 3 , Figure 3 The figure shows a schematic diagram of a calculation model of an amplitude-phase corrector under harmonic action in one embodiment of the present invention. This model is used to calculate component stress under various harmonics.

[0049] This embodiment can evaluate the stress of the amplitude phase corrector and its components under different voltage / harmonic conditions through the calculation model, including the system stress under normal and extreme working conditions and under the action of harmonics, and provide data support for the parameter design of the amplitude phase corrector. According to these two corrector parameter optimization models, the parameters of the amplitude phase corrector can be optimized to ensure that it can work normally under various working conditions, while improving the stability and efficiency of the system.

[0050] S2. Under different preset operation modes, respectively obtain impedance characteristics of the AC and DC systems of the target DC power transmission system topology.

[0051] This embodiment uses the AC busbar of the target DC power transmission system topology as a port to obtain the impedance characteristics of the system. Specifically,

[0052] Under different disconnection modes, a first impedance characteristic of the AC system within a preset frequency range is obtained; and under different operation modes, a second impedance characteristic of the broadband DC system is obtained.

[0053] It is understandable that a line break may cause a change in the impedance characteristics of the system, thereby causing problems such as harmonic resonance, so considering the impedance under the line break can achieve accurate selection of the amplitude and phase corrector parameters. In some embodiments of the present invention, the line break mode includes three line break modes of N-0, N-1 and N-2 within the three-level section.

[0054] Exemplarily, the following operations are included:

[0055] 1) Open the SLCC DC transmission system;

[0056] 2) With a step size of 5 Hz, the scanning range, i.e., the frequency range, is set at 0 to 2500 Hz, and different disconnection modes of N-0, N-1, and N-2 in the three-level section are considered.

[0057] The operation modes include bipolar operation, monopolar operation and monopolar metal operation, which will affect the current, voltage and other parameters of the DC system, thereby affecting its impedance characteristics.

[0058] The impedance characteristics can be obtained by determining the specific conditions of the disconnection mode or operation mode, such as the disconnection position, the number of disconnections, the operating power, etc. During the simulation process, simulation analysis is performed based on the constructed topological structure and mathematical model to obtain impedance characteristic parameters, such as impedance value, phase angle, etc.

[0059] S3. In response to the impedance characteristics, the component stress of the amplitude and phase corrector under the corresponding fluctuation state is obtained by simulating the amplitude and phase corrector parameter optimization model.

[0060] This step is the process of simulating parameters. According to the acquired impedance characteristics, the component stress of the power transmission system under different working conditions is simulated by the amplitude and phase corrector parameter optimization model.

[0061] It is understandable that when designing an amplitude-phase corrector, the stress tolerance of the components needs to be fully considered. If the stress of the component exceeds its tolerance, it may cause damage to the component or degradation of its performance, thereby affecting the overall performance of the amplitude-phase corrector. Based on this, this embodiment calculates the first stress distribution generated by the AC system under the extreme power frequency condition through the power frequency amplitude-phase corrector parameter optimization model.

[0062] And closing / opening the target switch in the harmonic amplitude and phase corrector parameter optimization model to obtain the second stress distribution generated by the AC system under the influence of harmonics. Figure 3 As shown,

[0063] When switches SW1-SW2 are closed and SW3 is open, the model represents the stress of the amplitude and phase corrector components caused by the harmonics generated by the converter;

[0064] When switches SW1-SW2 are open and SW3 is closed, the model represents the stress caused by the background harmonic voltage of the AC system.

[0065] In the model where stress is determined by the harmonic currents generated by the converter, the harmonic current I nc Multiply by a factor of 1.1 to accommodate the wider frequency range of the AC system and the component Z nF In the model where stress is determined by background harmonics, the AC system harmonic impedance Z nN The selection of is to make it and the amplitude and phase corrector impedance resonate continuously or nearly continuously at each background harmonic voltage frequency, so that the current flowing through the amplitude and phase corrector reaches the maximum value.

[0066] S4. In the corrector configuration link, the initial parameters of the amplitude-phase corrector are determined according to the voltage fluctuation rate of the AC system and the operating power range of the DC system, and the initial parameters are optimized based on the component stress to configure the amplitude-phase corrector.

[0067] In some embodiments of the present invention, by analyzing the structure, load characteristics and possible fault conditions of the power system, the voltage fluctuation range allowed by the system can be calculated, thereby determining the voltage fluctuation rate requirement. And by analyzing the operating characteristics of the DC system and the stability requirements of the power network, the operating power range of the DC system can be calculated. It can be understood that the voltage fluctuation rate should be controlled within 1%.

[0068] After determining the requirements for the voltage fluctuation rate of the AC system and the operating power range of the DC system, the parameters such as the reactive compensation required by the AC system under different operating powers can be calculated. That is, according to the calculation results, the initial parameters such as the base frequency reactive capacity of the amplitude phase corrector, the control strategy of the amplitude phase corrector, the response time and the adjustment range that can meet the reactive power requirements of the AC system are selected, and these parameters are used to configure the corresponding amplitude phase corrector.

[0069] Furthermore, in some embodiments of the present invention, during the configuration process, the component constants of the configured amplitude and phase corrector are calculated based on the harmonic parameters, that is, the acquired harmonic current and voltage, and the component constants are analyzed to optimize and adjust the parameters of the amplitude and phase corrector.

[0070] S5. After configuring the amplitude and phase corrector, repeat the corrector configuration step until the equivalent harmonic impedance of the target DC power transmission system topology meets a preset power transmission system oscillation index.

[0071] It can be understood that the equivalent harmonic impedance is a parameter that describes the impedance characteristics of the power transmission system at harmonic frequencies. Based on this, after configuring the amplitude and phase corrector, calculate whether the harmonic impedance of the AC system and the equivalent impedance of the DC power transmission system meet the system oscillation index. In some embodiments of the present invention, this preset power transmission system oscillation index may include oscillation frequency, amplitude, damping ratio, etc., which are used to evaluate the oscillation of the power transmission system under specific conditions.

[0072] Repeat the above configuration, evaluation and adjustment process until the equivalent harmonic impedance of the system meets the preset oscillation index. At that time, it can be determined that the configured amplitude and phase corrector can give full play to the impedance adjustment ability, suppress the harmonics generated by the system, and maintain the stable operation of the system.

[0073] In summary, this embodiment aims to optimize the amplitude-phase corrector parameters in the target DC transmission system topology to ensure that the equivalent harmonic impedance of the system meets the preset transmission system oscillation index; in response to the impedance characteristics of the AC and DC systems under different operating modes, a simulation analysis is performed through the designed amplitude-phase corrector parameter optimization model to obtain the component stress of the amplitude-phase corrector under the corresponding fluctuation state; in the corrector configuration link, the initial parameters of the amplitude-phase corrector are determined according to the voltage fluctuation rate of the AC system and the operating power range of the DC system. Then, the initial parameters are optimized based on the simulation results of the component stress to configure the amplitude-phase corrector. By optimizing the parameters of the amplitude-phase corrector, the harmonic oscillation in the DC transmission system can be effectively reduced, and the stability and reliability of the system can be improved.

[0074] An embodiment of the present invention provides a DC power transmission system impedance correction device, which is applied to a parameter design method of the DC power transmission system impedance correction device. For details, see Figure 4 , Figure 4 It is a schematic diagram of the structure of a DC power transmission system in one embodiment of the present invention, and it can be seen that the device includes: a multi-source adaptive DC power transmission system and an amplitude and phase corrector.

[0075] The multi-source adaptive direct current power transmission system comprises a grid phase-commutating converter, a commutating transformer and a filter; the amplitude-phase corrector is arranged at both sides of the multi-source adaptive direct current power transmission system.

[0076] It can be understood that the multi-source adaptive phase-commutated converter (SLCC) DC power transmission system of the embodiment of the present invention is a DC power transmission system combining a grid-commutated converter (LCC) and a large-capacity static VAR filter (SVF).

[0077] For example, Figure 4 As shown, the impedance correction device of the DC power transmission system in this embodiment is composed of two twelve-pulse LCC DC converter valves per pole, and an SVF is configured before each converter valve and converter transformer for valve-side reactive power compensation and filtering. Each twelve-pulse converter valve is configured with two three-phase SVFs, and the converter valve, SVF and converter transformer together constitute an SLCC converter. All converters at the sending end and the receiving end can be connected to the AC bus in layers (connected to the same AC bus in the figure), and the amplitude and phase corrector is connected to the AC bus on the AC side of the converter transformer.

[0078] Depend on Figure 5 As shown, Figure 5 The figure shows a schematic diagram of the structure of a C-type amplitude-phase corrector in one embodiment of the present invention. It can be seen that the amplitude-phase corrector is configured as a C-type amplitude-phase corrector composed of a high-voltage capacitor, a low-voltage capacitor, an inductor and a resistor connected in series and parallel.

[0079] It is worth noting that when calculating the harmonic current injected by the converter, the harmonic current generated by the LCC converter and the harmonic current filtered by the SVF should be considered comprehensively.

[0080] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A parameter design method for a DC power transmission system impedance correction device, characterized in that: include: According to the constructed target DC transmission system topology, the voltage and harmonic parameters of the AC system are obtained, and the amplitude and phase corrector parameter optimization model is designed; Under different preset operation modes, respectively obtaining impedance characteristics of the AC and DC systems of the target DC power transmission system topology; In response to the impedance characteristics, the component stress of the amplitude phase corrector under the corresponding fluctuation state is obtained by simulating the amplitude phase corrector parameter optimization model; In the corrector configuration link, the initial parameters of the amplitude-phase corrector are determined according to the voltage fluctuation rate of the AC system and the operating power range of the DC system, and the initial parameters are optimized based on the component stress to configure the amplitude-phase corrector; After the amplitude and phase corrector is configured, the corrector configuration step is repeated until the equivalent harmonic impedance of the target DC power transmission system topology meets a preset power transmission system oscillation index.

2. The parameter design method of the DC power transmission system impedance correction device according to claim 1, characterized in that: The design of the amplitude-phase corrector parameter optimization model includes: Under the power frequency extreme, design a power frequency amplitude-phase corrector parameter optimization model according to the acquired rated voltage, steady-state voltage, and extreme voltage of the AC system; A harmonic amplitude and phase corrector parameter optimization model is designed based on the acquired background harmonic voltage and harmonic current at the AC bus of the target DC power transmission system topology.

3. The parameter design method of the DC power transmission system impedance correction device according to claim 1, characterized in that: Under the preset different operation modes, the impedance characteristics of the AC / DC system of the target DC power transmission system topology are respectively obtained: Taking the AC bus of the target DC power transmission system topology as a port, obtaining a first impedance characteristic of the AC system within a preset frequency range under different disconnection modes; and Obtain the second impedance characteristics of the wideband DC system under different operating modes.

4. The parameter design method of the DC power transmission system impedance correction device according to claim 2, characterized in that: The step of simulating the component stress of the amplitude phase corrector in a corresponding fluctuation state by the amplitude phase corrector parameter optimization model in response to the impedance characteristic includes: In response to the impedance characteristic, a first stress distribution generated by the AC system under an extreme power frequency condition is calculated by using the power frequency amplitude and phase corrector parameter optimization model; The target switch in the harmonic amplitude and phase corrector parameter optimization model is closed / opened to obtain the second stress distribution generated by the AC system under the influence of harmonics.

5. The parameter design method of the DC power transmission system impedance correction device according to claim 1, characterized in that: The corrector configuration step also includes: Calculating component constants of the configured amplitude and phase corrector according to the harmonic parameters; The component constants are analyzed to optimize and adjust the parameters of the amplitude and phase corrector.

6. The parameter design method of the DC power transmission system impedance correction device according to claim 1, characterized in that: The voltage fluctuation rate is controlled within 1%.

7. The parameter design method of the DC power transmission system impedance correction device according to claim 3, characterized in that: The different disconnection modes include three disconnection modes of N-0, N-1 and N-2 within the three-level section.

8. The parameter design method of the DC power transmission system impedance correction device according to claim 3, characterized in that: The different operating modes include bipolar operation, monopolar operation and monopolar metallic operation.

9. A DC power transmission system impedance correction device, applied to the parameter design method of the DC power transmission system impedance correction device according to claims 1 to 8, characterized in that: The device comprises: a multi-source adaptive direct current power transmission system and the amplitude and phase corrector; The multi-source adaptive direct current transmission system includes a grid phase-commutating converter, a commutating transformer and a filter; The amplitude and phase correctors are arranged at both sides of the multi-source adaptive direct current power transmission system.

10. The DC power transmission system impedance correction device according to claim 9, characterized in that: The amplitude-phase corrector is configured as a C-type amplitude-phase corrector including a high-voltage capacitor, a low-voltage capacitor, a reactor and a resistor connected in series and in parallel.

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